Technical Field
The present invention relates to a light source device that emits light to an irradiation target, and an image projection apparatus employing the light source device.
Background Art
Screen images of personal computers, video images, and image data stored in memory cards can be transmitted to image projection apparatuses known as projectors that can project images onto a screen using a light source device. Meetings, presentations, and trainings are conducted using display devices having a large screen. Projectors are relatively inexpensive, and small and light weight, with which projectors can be carried easily, which means portability is good. Projectors are used frequently for meetings in small meeting rooms, meeting spaces set by partitions in offices with an increased demand for in-personal communication scenes and situations. Further, even if meeting rooms are not available, projectors can be used at open spaces such as passage, in which a projector can project images on a wall for a meeting.
As to the projectors, light emitted from a light source device is focused on a micro mirror display device known as a digital micro mirror device (DMD), or a liquid crystal plate, and then an image is displayed on a screen. As to the projectors, a high intensity discharge lamp such as high pressure mercury lamp is conventionally used as the light source, but other light sources have been developed. For example, a light source device employing the solid type light emitting element and phosphor has been available, in which the solid type light emitting element emits excitation light, and the phosphor, used as a wavelength convertor, absorbs the excitation light and coverts the light to a plurality of lights having different wavelength ranges. The solid type light emitting element can employ, for example, semiconductor elements such as a light emitting diode (LED), a laser diode (LD), or organic electroluminescence (OEL).
As to light source apparatuses employing a solid type light emitting element and phosphor, the phosphor used as a wavelength converter is disposed on a rotatable member, and a configuration for rotating the rotatable member is employed. As to this light source apparatus, a phosphor layer that generates heat when receiving excitation light from a light source can be cooled with an effect of rotation of the rotatable member.
However, if rotation of the rotatable member stops or decreases due to malfunction of a drive motor (i.e., when abnormality occurs to rotation condition), visible light emittable from the phosphor layer cannot be normally output to outside, light quantity of excitation light received by the phosphor layer on the rotatable member per unit time increases, and cooling effect by rotating the rotatable member decreases, with which abnormal temperature increase may occur to the phosphor layer.
If abnormal high temperature occurs to the phosphor layer, light having a designed wavelength range cannot be emitted, and light quantity of emission light may decrease greatly, with which deterioration of the phosphor layer may occur. Typically, a light source apparatus that can output light having higher power is employed to enhance image luminance projected by the projector. To output light having higher power from the phosphor layer, excitation light having greater power is required, in which abnormal high temperature may more likely occur to the phosphor layer, and deterioration of the phosphor layer may become prominent.
To cope with this situation, for example, when abnormality occurs to the rotation condition of the rotatable member, light emission of the light source is stopped to prevent deterioration of the phosphor layer. However, when light emission of the light source is stopped, display of a projection image by the projector also stops. Therefore, information such as occurrence of abnormality and a coping process to the abnormality cannot be informed to a user using a projection image by the projector. Other than using the projection image by the projector for informing abnormality, the information can be informed to a user by disposing a dedicated reporting unit used for reporting information. However, the dedicated reporting unit may become a capability-enhanced reporting unit to report detailed information to a user, which increases cost compared to a simple reporting unit such as a buzzer that generates alarm sound.